Latitude & Longitude issue

Please help -

I am attempting to create a Custom GPS Tour with Audio I have uploaded to this site. I drove to various locations that I'm including in my Custom GPS Tour while noting the Latitude and Longitude coordinates diplayed by my Garmin Nuvi 350 GPS. When I uploaded the Audio for my GPS Tour, I entered the Latitude and Longitude that my GPS displayed for each site. After creating my GPS Tour and copying the completed file to my GPS, the location is not the location I had entered. It's about 6 miles off. Am I doing something wrong?

Thank you for any help and/or ideas.